Introduction
The problem in following pages got attention. http://www.4clojure.com/problem/60#prob-title
solution
Here is my solution which passes the unit tests.
(fn myreduce
([f coll]
(when-let [s (seq coll)]
(myreduce f (first s) (rest s))))
([f v coll]
(lazy-seq (cons v (when-let [s (seq coll)]
(myreduce f (f v (first s)) (rest s)))))))